The importance of composite materials in the modern world can hardly be overstated. Composites in general can be thought of as a combination of two or more distinctly dissimilar components and include a wide range of products such as sandwich structures, laminates, reinforced polymers, concrete, and fiber reinforced components which achieve high-strength, stiffness, and durability that cannot be achieved alone by the individual components of the composite. Often, one of the components of such composites serves as the matrix in which particles or fibers of the other are uniformly dispersed like aggregate and concrete. In recent years, a new class of materials known as nano-composites has attracted great interest and research. These nano-composites offer properties not obtainable in the aforementioned conventional composites and allow the construction of tailor-made advanced composites.
The nano-composites are multi-phased materials containing two or more dissimilar components mixed on the nanometer scale. Particles of this size approach the range of 100 to 1000 times the size of a typical atom. These nano-composites exhibit new and often improved mechanical, catalytic, electronic, magnetic, and optical properties that are not possessed by their macro-composite or micro-composite counterparts. The reason for these different properties is not yet totally understood. Further description of many known nano-composites and their structures can be found in an article “Polymer Nano Composite Approach To Advance Materials” found in the Journal of Chemical Education, at Vol. 77, No. 9, 4 Sep. 2000, this article herein incorporated by reference. Accordingly, it is one of the general objects of the present invention to uniquely apply nano technology to composites that employ mineral and carbon fibers.
To bond inorganic materials such as mineral fibers or carbon fibers with organic materials, silane coupling agents are commonly used. These agents have the ability to form durable bonds between inorganic and organic materials and can bond dissimilar material where at least one of the members is siliceous or has surface chemistry with siliceous properties such as the silicates, aluminates, borates, and the like. The general formula for a silane coupling agent shows two classes of functionality.X(4−n)—Si—(R′R)n, (n=1,2)
X is a hydrolyzable group; typically alkoxy, acryloxy, halogen oramine. The X functional group is involved in the reaction with the inorganic substrate. The bond between X and the silicon atom in coupling agents is replaced by a bond between the inorganic substrate and the silicon atom. The most common alkoxy groups are methoxy and ethoxy, which give methanol and ethanol as byproducts during coupling reactions. Since chlorosilanes generate hydrogen chloride as a byproduct during coupling reactions, they are generally utilized less than alkoxysilanes.
R is a nonhydrolyzable organic radical that possesses a functionality which enables the coupling agent to bond with organic resins and polymers. Most of the widely used organosilanes have one organic substituent. R′ represents an alkyl bridge or spacer connecting the silicon atom and the organofunctional radical.
In most cases the silane is subjected to hydrolysis prior to the surface treatment. Following hydrolysis, a reactive silanol group is formed which can condense with other silanol groups, for example, those on the surface of siliceous fillers, to form siloxane Si—O—Si linkages. The silanol groups can also condense with other oxides—such as metal hydroxyl groups of aluminum, zirconium, tin, titanium, and nickel—to form stable condensation products (Si—O—M bonds). Less stable bonds are formed with oxides of boron, iron, and carbon. Alkali metal oxides and carbonates do not form stable bonds with Si—O—.
The final result of reacting an organosilane with a substrate ranges from altering the wetting or adhesion characteristics of the substrate, utilizing the substrate to catalyze chemical transformations at the heterogeneous interface, ordering the interfacial region, and modifying its partition characteristics. Significantly, it includes the ability to effect a covalent bond between organic and inorganic materials. The interfaces involving such materials are modified in order to incorporate the flow properties of the material forming the composite structure. Thus, the use of the silane or organosilane coupling agents on mineral surfaces such as fiberglass will bond a polymeric surface such an epoxy or fluorocarbon to the glass surface.
One of the nano-materials of particular interest is nano-silica. An abstract reported in the Journal of Dispersion Science and Technology, Vol. 25, No. 6/20004 at pp. 837 to 848, herein incorporated by reference, reported on the grafting of nano-silica particles with a specific modification agent. In another article entitled “HLDPE/Organic Functionalized SiO2Nano-composites With Improved Thermal Stability And Mechanical Properties” (also incorporated herein by reference) it is reported that addition of pretreating nanosilica with organic multifunctional modifiers lead to an increase of thermal stability, elastic modulus, and toughness.
Accordingly, it is a specific object of the present invention to incorporate the beneficial properties of nano mineral particles in finishes for yarns and fabrics of mineral and carbon fibers.
The invention will be better understood by reference to the Summary of the Invention and Detailed Description which follow.